When researchers boast rather casually that making new variations of their invention is as simple as editing a CAD file, we might assume they are talking about a new sort of coffee mug, or perhaps a revolutionary spool for a garden hose. Certainly such a simple and cost-effective design process could never give rise to something as complex as a bio-robot, a chimera of industrial gel and living tissue designed to work inside the human body. However, after researchers at the University of Illinois set themselves the task of creating just such a robot, that’s precisely what they did.

Using new, specialized 3D printing technology, engineers were able to deposit a bio-friendly hydrogel into a cantilever design just seven by two millimeters in size, seeded with heart cells from a rat. The cells grew into a matrix and began doing what heart cells do best — beating. By depositing the cells in a particular arrangement throughout the structure, and coaxing them to grow in the desired ways, the beats eventually produced controlled forward movement. After a number of false starts and inferior designs, the researchers were able to build a bio-robot that moved consistently — albeit at only 236 micrometers per second, or 0.00053 miles per hour.

Theik workflow allowed the team to create an array of prototypes that they used determine the optimal length and thickness of the biobot’s actuating leg, which provides the power to drive the whole thing forward. In under a dozen prototypes, both CAD-designed and machine-printed, researchers found a working midpoint between the flexibility and strength of the actuating leg, as well as between the stability and size of the support leg.